Typically, stents are tubular devices that are delivered into a patient's vascular system via a catheter or similar delivery device. Stents can be used to treat a variety of different conditions, including stenosis and aneurysms. When used to treat stenosis (narrowing of a vessel), the stent is used to press against thrombus and open a vessel to allow normal blood flow. When used to treat aneurysms, low-porosity stents can be used to limit blood flow to a vessel (so-called flow-diversion stents) to promote clotting of the aneurysm and reduce the risk of aneurysm rupture. Alternatively, the stent can be used as a scaffold to keep other embolic material (such as embolic coils) within the aneurysm.
When a stent is deployed in a generally linear portion of a vessel, stent delivery is typically straightforward. For example, a distal end of a delivery catheter is advance near a desired delivery location and the outer sheath is withdrawn, allowing the stent to expand within the vessel. Even in these linear vessel situations though, stent delivery can still be challenging due to variables such as the size of the stent, size of the delivery catheter, and size of the vessel. Often, when the stent must be deployed at or near a tortuous or heavily curved portion of a vessel, a self-expanding stent may have difficulty properly deploying. For example, FIG. 1 illustrates a self-expanding stent 12 (e.g., such as that described in U.S. Pat. No. 9,439,791, incorporated herein by reference in its entirety) being deployed in a heavily curved portion of a vessel 10. While the catheter 14 releases the stent 12, it forms a flat or collapsed portion 12A against the outer curved surface of the vessel 10. FIG. 2 illustrates a second flat or collapsed portion 12A formed against the outer surface of a second curve of the vessel 10 as the stent 12 is further expanded. When collapsed portions 12A occur, the physician's only alternative is to attempt to rotate the catheter 14 and/or partially retract and re-deploy the stent 12.